• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.346-346
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• 2007

압전세라믹 재료는 현재 압전 변압기, actuator, transducer, sensor, speaker 등에 광범위하게 이용이 되고 있다. 이 중에서 압전세라믹 소결체를 이용한 스피커의 제조는 가공이 까다롭고, 대형의 크기로 제작 시 소자가 깨지는 등의 많은 제약을 받고 있으며, 저음 특성이 떨어져 응용 범위가 한정되어 있다. 따라서 최근에는 이러한 단점을 극복하기 위하여 세라믹/고분자 복합체를 이용한 필름 스피커를 제작하고자 시도하고 있다. 이러한 세라믹/고분자 0-3형 압전 복합체를 이용할 경우, 제품의 경량화를 실현할 수 있고, 크기나 환경의 영향을 거의 받지 않으므로, 고기능성 스피커로의 응용에 적합할 것으로 보인다. 따라서 본 연구에서는 PZT계의 세라믹와 PVDF, PVDF-TrFE, Polyester, acrylic resin 등의 여러 고분자 물질과의 복합체를 제조하여 압전특성을 평가하였다. 본 실험은 먼저 $(Pb_{1-a-b}Ba_aCd_b)(Zr_xTi_{1-x})_{1-c-d}(Ni_{1/3}Nb_{2/3})_c(Zn_{1/3}Nb_{2/3})_dO_3$ (이하 PZT라 표기)의 최적화 조성을 선택하여, $1050^{\circ}C$에서 소결된 분말을 48시간 ball milling방법 로 약 $1{\mu}m$ 크기로 분쇄하였다. 고분자 물질들은 알맞은 용제들을 선택하여 녹였다. 그 다음 소결된 PZT분말과 고분자를 50:50, 60:40, 65:35, 70:30등의 무게 분율로 혼합하고, 분산제, 소포제 등을 첨가하여 3단 roll mill을 이용하여 충분히 분산시켜 페이스트 (Paste)를 제조하였다. 제조된 페이스트를 ITO가 코팅된 PET필름 위에 스크린 프린팅 법을 사용하여 인쇄하여 $120^{\circ}C$에서 5분간 건조하였다. 코팅된 복합체의 두께는 약 $80{\mu}m$ 정도로 측정되었다. Ag 페이스트를 이용한 상부 전극 형성에도 스크린 프린팅 법을 적용하였다. 이를 $120^{\circ}C$에서 4 kV/mm의 DC 전계로 분극 공정을 수행한 후 전기적 특성을 평가하였다. 유전특성을 조사하기 위해서 LCR meter (EDC-1620)를 사용하였고, 시편의 결정구조는 XRD (Rigaku; D/MAX-2500H)을 통해 분석하였으며, 전자현미경(SEM)을 이용하여 미세구조를 분석하였다. 압전 전하상수$(d_{33})$ 값은 APC 8000 모델을 이용하여 측정하였다. PZT의 혼합비가 증가할수록 비유전율 및 압전 전하 상수 등의 전기적 특성이 증가되었다. 또 여러 고분자 물질 중에서 PVDF-TrFE 수지가 가장 우수한 특성을 보였다. 이는 PVDF-TrFE 수지가 압전성을 나타내기 때문인 것으로 판단되었다.

• Journal of Korean Institute of Fire Investigation
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• v.6 no.1
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• pp.49-66
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• 2005

The purpose of this study is to present reference data to be considered in designing fur the fire safety of atrium buildings. This study deals with the characteristics of atrium buildings in the fire safety aspect, analysis of fire examples and foreign fire codes of atrium space. And con-crete factors to be consigning fur the fire facilities of atrium buildings are presented. Recently many atrium spaces have been built in Korea. They provide new experience of space with resident and pedestrians. However, because of the lack of knowledge in design principle and disaster prevention, large loss of lives is expected in an emergency situation. cion. Therefore safety ensuring from the case is urgently needed. The following is the summary on the standard of effective fire facilities for the atrium. 1. The smoke control. inside atrium must use the machine ventilation in the atrium. 2. It is desirable to divide the section between atrium and nearby living room by anti-smoke screen in order to prevent damage by smoke when fire break out. 3. It is desirable to instill an excellent fire detector like infrared light detector as a replacement of old one. 4. It is desirable to transfer from closed operating sprinkler to fire-cycle sprinkler equipment or ablative sprinkler when the height is lower than 20m.

• Journal of radiological science and technology
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• v.28 no.1
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• pp.1-7
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• 2005

High-quality single crystals of pure $Li_2B_4O_7$ as well as $Li_2B_4O_7$ doped with Cu, Mn and Mg impurities (1.0mol%, respectively) have been grown from the melt of $Li_2CO_3+2B_2O_3$ by Czochralski method in platinum crucibles. To study the thermoluminescent properties, $Li_2B_4O_7$ series single crystal TLDs were made by cutting in the size of $4{\times}5{\times}1\;mm^3$. The glow curves show two or three peaks which can be easily deconvoluted. It is observed that room temperature($20{\sim}30^{\circ}C$) fadings of the dosimetric peaks of $Li_2B_4O_7$ series single crystal TLDs were about 10 % for 30 days. The relative photon energy response for $Li_2B_4O_7$ series single crystal TLDs were about 85 % when the responses were normalized to that measured with $^{60}Co\;(1.25\;MeV)\;{\gamma}-rays$. The measured data are in a good agreement with theoretical ones. The $Li_2B_4O_7$ series single crystal TLDs fabricated in this work can be used for monitoring personal and environmental radioactivity.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.5-11
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• 2006

Urinalyses have been conducted for 28 seamen in K University's training ship and Creatine and Uric acid turned out to be higher in all ages, which can be inferred that on-deck environment has caused negative impact on kidney and/or malfunction. In addition, TC arid HDL-C, LDL-C has decreased, however, TG has increased after the navigation. All different positions including oater, crew, decker, engineer and radio part showed the similar pattern. TC and HDL-C has decreased in 30s, 40s and TG has increased in 30s. A few of the 30's show extremely high TG rates so Hyperlipidemia is suspected. 7 members fumed out positive for UBG test and 5 positive for PRO test. Especially there was only one UBG positive before the navigation but, 7 members has become positive, which means the one-month ocean navigation has definite impact on the liver cell function.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.19-27
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• 2006

The purpose of this study was to find of morbidity rate and pattern of disease and affect of variables related disease and medical management of seafares' The subjects this study were 1049 seafares' who took education in Korea Institute of Maritime and Fisheries Technology. This questionnaire was focused on finding the basic data for prevention of disease and promotion health for the seafares' The collected data were analyzed by using descriptive statistics, Chi-square, cross tab, linear regression by SPSS 10.1 package. The result of this study are as follow. 1)The morbidity rate within recent 12 months was 69.0%. 2)there were significant differences of occurred disease in age(p<0.05), income(p<0.01), career of ship on board(p<0.01), rank(p<0.01), perceived health status(p<0.01), worry of health(p<0.01), fatigue symptoms(0.01), satisfy of job(p<0.05), rest time(p<0.05) 3) Considering disease unable to work more than 4 hour, the number of those who had oral disease 7.3%> tinea 6.6%> gastric ulcer 6.4, and musculoskeletal disease group were 20.9%, which revealed the highest rate oral disease 13.6%> skin disease> 12.4%, digestive disease> 12.1%. 4) As refer to medical management, The pain above 31days 35.7%, hospitalization and treatment below 7days were each 50.2%, 42.8%, medical service were doctor's office 27.9, which revealed the highest rate.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.29-38
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• 2006

The purpose of this study was to find out morbidity rate and pattern of occupational disease and affect of variables related disease of Fishing sailors' The subjects this study were 624 fisheries sailors' who took education course in Korea Institute of Maritime and Fisheries Technology. This questionnaire was focused on finding the basic data for prevention of occupational disease and promotion health on the fishing sailors' The collected data were analyzed by using descriptive statistics, Chi-square, cross tab by SPSS package. The result of this study are as follow. 1)The morbidity rate within recent 12 months was 70.2%. there were significant differences of occurred disease in age, rank, perceived health status, fatigue symptoms, rest time, workload, overtime duration 2) the more aging(p<0.01), perceived fatigue(p<0.01), workload(p<0.01), overtime(p<0.05) and the less perceived health status(p<0.01), rest time(p<0.01), the higher morbidity rate 3) Considering disease unable to work more tlnn 4 hour, the number of those who had musculoskeletal disease were 20.9%, which revealed the highest rate, digestive disease 14.3%, traumatic disease 13.5%.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.21-31
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• 2014

Recently, the research on renewable energy against depletion of fossil fuel have been actively carried out in the world. Especially, offshore wind turbines are very economical and innovative technology. However, offshore wind turbines experience large base moments due to the wind and wave loading, so the monopile with large diameter needs to be applied. For the economical design of the large diameter pile, it is important to consider the flexibility of the foundation to estimate the maximum moment accurately, based on studies conducted so far. In this paper, the foundation was modeled using the finite element method in order to better describe the large diameter effect of a monopile and the results were compared with those of p-y method. For the examples studied in this paper, the change in maximum moment was insignificant, but the maximum tilt angle from the finite element method was over 14% larger than that of p-y method. Therefore, the finite element approach is recommended to model the flexibility effect of the pile when large tilt angles may cause serviceability issues.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.4
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• pp.490-496
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• 2008

The purpose of this study was to examine the qualities of breads added with 0.01%, 0.1% and 1% of Sargassum siliquastrum extracts (SSE). The result of total microbial count showed that breads with SSE were reduced with increasing storing time, especially bread with 1% SSE was reduced about 2 log cycle as compared to that of control. The moisture content of the bread added SSE and non-added bread were not significantly different during the early storage period, but after 9 days of storage, the moisture content of control was 13% decreased while that of the SSE added bread was decreased by only $5{\sim}6%$. In the color, lightness and yellowness of bread diminished with increasing amounts of SSE in bread while conversely, redness increased. In sensory evaluation, bread containing 0.01% and 0.1% SSE were preferred than the control over total preference, while bread containing 1% SSE showed the lowest preference. These results suggest that the addition of 0.1% SSE in bread had a good effect on improving the preservation and development of quality.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.138-141
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• 2004

[ $MnO_2$ ]가 첨가된 $0.9Pb(Zr_{0.5}Ti_{0.5})O_3-0.2Pb[(Zn_{0.8}Ni_{0.2})_{1/3}Nb_{2/3}]O_3$(0.8PZT-0.2PZNN) 세라믹스는 그 압전특성과 유전특성이 뛰어나지만 $1000^{\circ}C$ 이하의 낮은 소결 온도에서는 소결되지 않는다. $1000^{\circ}C$이하의 낮은 소결온도에서 소결하기 위해 CuO를 첨가한 결과, 소결온도 $920^{\circ}C$에서 소결성은 우수하였으나 그 압전 특성의 저하가 두드러졌다. 이는 XRD에서 확인한 결과에 따르면 CuO의 첨가가 우수한 MPB 조성으로 판명된 $MnO_2$ 가 첨가된 0.8PZT-0.2PZNN 세라믹스의 결정구조를 Rhombohedral 구조로 바꾸기 때문인 것으로 보였으며 이러한 문제는 PZNN의 비율을 조절하여 0.875PZT-0.125PZNN 세라믹스를 선택함으로 인해 해결할 수 있었다. 그러나 여전히 낮은 $Q_m$값을 높이기 위해서 $Al_2O_3$를 첨가하였고 그 결과 시편의 tetragonality 감소와 $Q_m$값의 증가를 확인할 수 있었으나 그 첨가량이 0.2wt% 이상일 경우에는 밀도의 감소로 인한 압전특성의 저하가 나타났다. 밀도의 향상을 위해 Zn and Ni excess 조성을 선택하였고 그 결과 0.5wt% $MnO_2$와 0.2wt% CuO 그리고 0.3wt% $Al_2O_3$를 첨가한 0.875PZT-0.125PZNN 세라믹스(Zn and Ni excess 조성)를 $920^{\circ}C$에서 소결한 경우 $k_p=0.581,\;Q_m=809,\;d_{33}=345\;pC/N\;and\;{\varepsilon}_{33}/{\varepsilon}_0=1345$의 빼어난 압전 및 유전특성과 $330^{\circ}C$의 높은 $T_c$를 보였고 그 조성의 vibration velocity는 약4.5 m/s로 나타났다.

• Journal of radiological science and technology
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• v.29 no.2
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• pp.71-74
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• 2006

We analyzed retrospectively our experience to evaluate an effect of extracorporeal shock wave lithotripsy (ESWL) for renal stone with infundibular stenosis. From January 2002 to August 2005, 35 patients with renal stone with infundibular stenosis were treated with ESWL. The diagnosis of infundibular stenosis was made by intraveneous pyelography or retrograde pyelography. The final follow-up check was performed by simple abdominal film or computed tomography and interview after 6 months to 24 months (mean 10 months). 7(20.0%) of 35 patients was freed completely, but Stone free rate including less than 2 mm size was 80%(28/35). 30(85.7%) patients became asymptomatic, 4(11.4%) patients were continued, and 1(2.9%) patient was required the percutaneous nephrostolithotomy. Although ESWL has a low complete stone free rate, We suggest that renal stone with infundibular stenosis should be treated with ESWL, because that is likely to produce a high symptom free and low complications.